Not only a constituent material composed only of a metal material such as copper but also a composite material made of a metal and a non-metal inorganic material (representatively, ceramics), such as Al-SiC, have been made use of as a constituent material for a heat radiation member (a heat spreader) to be attached to a semiconductor element. Mainly aiming to achieve lighter weight of a heat radiation member, a magnesium-based composite material including magnesium (Mg) which is lighter in weight than aluminum (Al) or an alloy thereof as a base material has recently been studied (see Japanese Patent Laying-Open No. 2006-299304 (PTL 1) and Japanese Patent No. 4594433 (PTL 2)).